It is generally known to use latch devices for locking pieces of air freight such as freight containers in the X-direction, in a freight loading and securing system installed in the freight or cargo hold of an aircraft. The X-direction is parallel to the lengthwise roll axis of the aircraft, while the Y-direction is parallel to the crosswise or lateral pitch axis of the aircraft, and the Z-direction is parallel to the vertical or yaw axis of the aircraft. Such X-direction locking devices or X-latches are typically installed on the roller tracks or contact rails which are provided for supporting the freight containers and which extend in the lengthwise or X-direction of the aircraft. However, in order to install such known X-latches, significant work effort and revisions are required in the other existing components of the freight securing system. Furthermore, the structure of the freight securing system must be reinforced or strengthened in the area below the roller tracks, and particularly the connections thereof to the aircraft structure, in view of the additional loads transmitted through the X-latches.
German Patent Publication DE 4,021,499 C1 and corresponding U.S. Pat. No. 5,090,638 (Eilenstein-Wiegmanns et al.) discloses a locking mechanism for securing freight pieces in the freight hold of an aircraft. The known locking mechanisms are respectively arranged in a housing that can be selectively installed in recesses provided at various locations or positions in the freight loading floor of the freight hold. While a piece of freight such as a freight container can roll over the known locking mechanism in one direction, whereby the locking mechanism is automatically pushed down into a recessed position, in order to roll the freight over the locking mechanism in the other direction, the mechanism must be recessed down into its housing. The known locking mechanism comprises a latching member that is pivotally mounted in the housing, and a latch operating member connected to the latching member via a cam and guide track arrangement and a tension spring. Two stop members are provided respectively on the latching member and the latch operating member to prevent the latching member from tilting if the latch operating member has not previously been operated or repositioned. While this known latching or locking mechanism effectively achieves its intended objects and functions in actual practice, it has been found that the structure and installation of an X-direction locking mechanism can and should still be simplified. It is especially desirable to simplify an X-locking device in such a manner that it can more easily be retrofitted into existing freight loading and securing systems, without requiring recessed floor pockets and without requiring reinforcement of the original structures.